Building a 15 kW Swimming Pool Heater from Solar Surplus

Steps

1. 1

   Step 1: Stripping the original electronics and housing

   Watch this part (3:52)

   I start by removing the screws at the back and near the display to take off the hard-to-remove housing. Inside, I find the compressor, the cold side of the radiator, and the warm side at the bottom where the water runs. Water often gets onto the power plug, runs down into the casing, and destroys the controller from underneath.

   Since the controller is screwed in from the bottom, I just break it off to get to it. I no longer need any of the original circuitry, reset buttons, control boards, or temperature sensors.

2. 2

   Step 2: Rewiring the compressor and fan separately

   Watch this part (5:28)

   After cutting away the old controller, I remove the power cable by cutting it off to make the system safer with fewer cables. I drill two holes in the side, making sure not to hit the internal air conditioning lines, and push a new power cable inside. The fan uses two black wires, which I connect to the new power cable using terminal blocks, and I attach its earth wire to the metal casing with a crimped eyelet.

   I mark this fan cable with a piece of green insulation tape so I can easily identify it later. Then I connect another power cable to the red and blue wires of the compressor and put the housing back together.

   Warning

   Watch out for internal air conditioning lines when drilling holes in the side of the casing.

3. 3

   Step 3: Testing individual components

   Watch this part (9:38)

   With the modifications complete, I can now control the fan and compressor independently. I test the fan by plugging its green-taped cable into a temporary test cable, which immediately makes the loud fan spin. Next, I test the compressor by plugging in its cable, and I can hear it humming and the gas hissing, which confirms the system works.

   I repeat this entire modification process on all three heat pumps while hunting for two more cheap units on Marktplaats.

   Warning

   Do not run the compressor for too long without the fan running and without water flowing through it, because it cannot cool itself.

4. 4

   Step 4: Installing a dimmer for the fan

   Watch this part (13:02)

   The heat pump fans make a lot of noise, so I use a small, cheap dimmer to turn down the motor's rotational speed and make it significantly quieter. I connect the green fan cable's neutral and live wires to the dimmer, and put a normal plug on the dimmer's input. Dimming the motor slows it down and reduces the noise for the neighborhood, and although its efficiency drops a tiny bit, I do not mind because I am using free solar surplus energy.

   What I used

   Item	Amount	Notes
   dimmer	1	Small and cheap motor speed controller

5. 5

   Step 5: Mounting the heat pumps on a trolley with TPU feet

   Watch this part (14:55)

   Because stacking five heat pumps on top of each other will become extremely heavy, I place a wooden platform on a trolley cart to hold them. The heat pumps have a curved top, so I provide 3D designs for replacement feet that you can print in TPU and glue underneath to make them level.

   What I used

   Item	Amount	Notes
   trolliewagentje	1	Trolley cart for mobility
   wooden platform	1	Mounted on the trolley
   TPU feet	multiple	3D printed replacement feet for the bottom

6. 6

   Step 6: Wiring multiple fans to the dimmer and Wago blocks

   Watch this part (15:30)

   I mount an electrical junction box on the side of the setup for the wiring. A main power cable comes in at the bottom and splits using three Wago blocks for earth, live, and neutral. The live and neutral feed the input of the dimmer, and the dimmer's output goes to another set of three Wago blocks that connect to all the fan wires.

   I also connect all the fan earth wires together and link them to the main plug's earth.

   What I used

   Item	Amount	Notes
   elektrodosje	1	Electrical junction box mounted on the side
   Wago blocks	multiple	Used to split power lines

7. 7

   Step 7: Installing toggle switches for the compressors

   Watch this part (18:29)

   I install five toggle switches inside the casing, which are rated for 6 A max, making them more than enough for the heat pumps. I connect all the switches to a permanent live wire from the incoming main power cable. Then I connect the live wires coming from the compressors to the back of each toggle switch, while connecting all the compressor neutral wires to the main neutral distribution block.

   What I used

   Item	Amount	Notes
   toggle switches	5	AliExpress switches rated for 6 A max

8. 8

   Step 8: Testing the multi-unit switch setup

   Watch this part (20:15)

   With everything wired up, I plug the main power cable into the outlet and test the system. When I turn the dimmer knob, the fan motors spin up, and I can adjust them to a quieter speed without blowing everything off the table. Then I test the toggle switches one by one to make sure each compressor kicks in properly.

   Later, I plan to link these switches to my smart home system so that as my solar panels export more power, more heat pumps automatically turn on.

9. 9

   Step 9: Connecting insulated water hoses

   For the water lines, I use 23 mm pool hoses that are flexible, rubber, and have a long lifespan, secured with 32 mm hose clamps. I wrap a bit of insulation tape around the ends of the pump connections because my personal experience shows it seals even better than a rubber ring. Since the fans blow out freezing cold air that would cool down the water inside the hoses, I slide foam insulation pipes over the pool hoses to protect them from the cold draft.

   What I used

   Item	Amount	Notes
   pool hose	multiple	23 mm flexible rubber hose
   hose clamps	multiple	32 mm size
   isolation tape	1	Used around pump connections for a better seal
   isolation pipe	multiple	Foam insulation tubes for the hoses

10. 10

    Step 10: Takeaways

    • Used Hot Splash heat pumps have a design flaw where water gets behind the display sticker and ruins the circuit board.

    • Removing the original faulty electronics allows manual control of the compressor and fan.

    • A cheap motor dimmer makes the loud cooling fans much quieter for the neighborhood.

    • Foam insulation tubes protect the water hoses from being cooled down by the fan exhaust.

    • Three connected heat pumps successfully heated 12 cubic meters of pool water by 10 to 11 degrees in less than a day.